Mexico's state-owned oil company says it has found two more bodies amid the rubble of a headquarters building damaged by a still-unexplained blast.

The find raises the death toll of Thursday's explosion to 35 people.

Petroleos Mexicanos operations director Carlos Murrieta had said that rescue crews were looking in the rubble for several more people reported missing, and believed their bodies were in the building's most damaged part.

The bodies of two of the four more people reported missing by their relatives were recovered Sunday.

Officials still have not given any cause for the explosion, though they have said they suspect it was an accident. The blast also injured 121 people.

Rescuers had initially concluded their search Friday but resumed operations when they suspected more bodies were in the rubble.